Final answer:
The chemical potential of the vapor and liquid phase of a substance at equilibrium is equal, with both phases reaching a state where the vapor pressure remains constant regardless of ongoing vaporization and condensation.
Step-by-step explanation:
At equilibrium, the chemical potential of the vapor and liquid phase of a substance is equal. This is because at the boiling point inside a closed system the rates of boiling (molecules leaving the liquid phase to become vapor) and condensation (vapor molecules returning to the liquid) are equal, so there is no net change in the amounts of the two phases.
As a result the system reaches a state where the vapor pressure remains constant signifying that the two phases are in equilibrium. Even if we increase the temperature equilibrium can still be maintained, but with increased rates of boiling and condensation. It's important to note that the equilibrium vapor pressure is a characteristic feature of the material and is affected by temperature and the intermolecular forces present. The vapor pressure doesn't depend on the amount of the liquid as long as some of the liquid is present alongside the vapor in the closed system.